1. Field of the Invention
The present invention relates to a field effect semiconductor laser, a method of modulation thereof and a method of making the same, and especially the one where an oscillation condition of the semiconductor laser can be directly controlled by an external control voltage applied thereto.
2. Prior Art
In a conventional semiconductor laser, in order to modulate an oscillation signal of the semiconductor laser, a current supplied to the semiconductor laser was changed, thereby modulation of a laser light corresponding to the change of the current was obtained. However, in such a conventional semiconductor laser of a current driving type, the switching speed was limited to several GHz.
On the other hand, a new device including a semiconductor laser and a field effect transistor in one chip has been already proposed, e.g. by Ury et al., American Institute of Physics, Appl. Phys. Lett. 34(7), Apr. 1, 1979, p. 430 to 431.
In such device, a current passing through a pn junction of the semiconductor laser is made by a channel current of the field effect transistor, thereby oscillating strength of the device can be changed by the gate voltage of the field effect transistor. However, in this device, since the oscillation condition is indirectly changed through the FET, its switching speed is not so high, and the structure of the device is very complex.